Adler E, Stuchin S A, Kummer F J
Department of Bioengineering, Hospital for Joint Diseases Orthopaedic Institute, New York, NY 10003.
J Arthroplasty. 1992 Sep;7(3):295-301. doi: 10.1016/0883-5403(92)90052-r.
Mechanical tests were performed to characterize the initial stability of press-fit cups as a function of cup design, surface structure, and surgical preparation. Eight cups from six manufacturers were press-fit into acetabular cavities prepared in two densities of Sawbones polyethylene foam and in bovine knee trabecular bone. Cavity sizes and cup loading forces were varied. Acetabular defects were simulated in the Sawbones model. Preparations were tested to determine axial-rotatory and tangential ("levering-out") stability. Results suggested that cup geometry and proper surgical technique--in particular, proper sizing and depth of the acetabular cavity--are important in determining initial cup stability independent of adjuvant screw or spike fixation. Stability is a function of the area of interface contact between the cup rim and the substrate. If the cavity is too small or too shallow, and the substrate too dense, the cup will not seat to the rim and stability will be compromised. If there are defects in the rim, the area of interface contact will be diminished and stability compromised. Cups with a true hemispherical design have a greater area of rim interface contact than "low-profile" cups and are therefore more stable. 1 mm undersizing of the cavity (or 2 mm undersizing in less dense substrate) appears to provide optimal stability.
进行了力学测试，以表征压配髋臼杯的初始稳定性与髋臼杯设计、表面结构和手术准备的关系。来自六个制造商的八个髋臼杯被压配到两种密度的Sawbones聚乙烯泡沫以及牛膝关节松质骨中制备的髋臼腔中。髋臼腔尺寸和髋臼杯加载力有所变化。在Sawbones模型中模拟髋臼缺损。对这些准备进行测试，以确定轴向旋转和切向（“撬出”）稳定性。结果表明，髋臼杯几何形状和适当的手术技术——特别是髋臼腔的适当尺寸和深度——在确定髋臼杯初始稳定性方面很重要，与辅助螺钉或钉固定无关。稳定性是髋臼杯边缘与基底之间界面接触面积的函数。如果髋臼腔太小或太浅，且基底太致密，髋臼杯将无法与边缘贴合，稳定性将受到影响。如果边缘有缺陷，界面接触面积将减小，稳定性也会受到影响。具有真正半球形设计的髋臼杯比“低轮廓”髋臼杯具有更大的边缘界面接触面积，因此更稳定。髋臼腔尺寸小1 mm（或在密度较小的基底中尺寸小2 mm）似乎能提供最佳稳定性。
